Pulse-producing apparatus for calibrating detonation meters



April 8, 1958 K. A. MGcoLL'oM ETAL 2,830,191

PULSE-PRODUCING APPARATUS FOR CALIBRATING DETONATION METERS Filed NOV. 5 1951 2 Sheets-Sheet 1 vvv INVENTORS. N K A MC coLLoM v BY #ubid/'1m M o R DE Bo|sBLANc AUoR/vfrs yApril s, 195s K' MCCOLLOM ET*- 2,830,191

PULSE-PRODUCING APPARATUS FOR CALIBRATING DETONATION METERS Filed Nov.l 5. 1951 Y 2 Sheets-Sheet 2 2o 2o B 2o FIG. 3a

l/23 I/s l 23 I IEA E4 I FIG. 3b

FIG. 3c

I\23q I I`23d FIG. 3d

. FIG. 3e A 23h 24o 24d 23h 24d \I I/ I/ \I IN VEN TORS K.A. MC COLLOM BY D.F\. DE BOISBLANC United States Patent f PULSE-PRODUCING APPARATUS FoR CALI- BRATING DEroNATIoN METERS Kenneth A. McCollom and Deslonde R. De Boisblanc, Idaho Falls, Idaho, assgnors to vPhillips Petroleum Company, a corporation of Delaware Application November 5, 1951, Serial No. 254,962

` 6 claims. (ci. 25o-214) `'This invention relates to a circuit and apparatus for producing spaced sets of pulses. In another aspect, it relates to a circuit for calibrating a detonation meter.

In the copending application of Kenneth A. McCollum et al., led April 19, 1951, Serial No. 221,928, now Patent 2,715,832, granted August 23, 1955, entitled Engine Analyzer, and in the copending application filed October 31,1949, Serial No. 124,667, now Patent 2,679,746, granted June 1, 1954, to D. R. de Boisblanc, entitled Detonation Analyzer, there is shown an instrument for determining the time interval Vbetween the occurrence of detonation in ankinternal combustion engine and a reference time occurring during each cycle of cylinder operation. Preferably andadvantageously, the reference time can be the time at which the spark impulse occurs in the cylinder under test. In this case, the interval measured is that between the occurrence of the spark and the occurrence of detonation during each cycle of cylinder operation. Alternatively, the reference time can be the time at which the low frequency wave representing the rate of change of pressure in the cylinder due to normal burning of the fuel reaches its maximum value. In this case, the interval measured is that between the time of occurrence of said maximum value and the time of occurrence of detonation during each cycle of cylinder operation.

In order to calibrate this detonation measuring instrument, it is desirable to produce a number of sets of pulses, each corresponding in duration to one cycle of cylinder operation of a test engine under standard conditions. Each set consists of two pulses, one representing the time of occurrence of the detonation and the other representing the time of occurrence of the index variable, which can be the spark, or the time of occurrence of the maximum value of the rate of pressure change. When these two pulses in each set are spaced along the time axis a predetermined distance apart, the output of the calibrating device can be fed to one of the aforementioned detonation-measuring instruments to eiect a quick and accurate calibration thereof.

Although it is a major purpose of our invention to provide such a Calibrating device, various combinations of circuit elements and mechanical parts described and claimed in this application'have independent utility in other elds, as those skilled in the art will understand.

It is an object of the invention to provide a circuit for Calibratingy a detonation measuring instrument which measures the time interval between the occurrence of detonation and a reference time during each cycle of cylinder operation.

It is a further object to provide a pulse-producing circuit of novel and improved character.

It is a still further object to provide a circuit which is simple in construction, reliable in operation, andhas a minimum number of standard circuit components.

LVarious other objects, advantages and features of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

Ice

' ordinate representing amplitude.

Referring now to Figure 1, a light beam is produced by a source 10, preferably a point source, therbeam being focused by a lens 11 upon a photoelectric cell 12. The

lens 11 has such properties that the lighty beam passing therefrom consists, effectively, of parallel rays. Interposed in the path of the light beam is a circular shutter 13 mounted upon a rotatable shaft 14 which is driven by Y a motor 15. Shutter 13 is provided with a series of slots 16a,-16b and 16e which are spaced at equal angular intervals about the circumference of the shutter. The walls 17 defining the slots lie along radii of the shutter 13. As a result, the output of photoelectric cell 12 is a series of rectangular waves, the leading edge of which is lproduced when one of the radially extending walls 16a of a given slot moves out of the path of the light beam,

and the trailing edge being produced when -the other radially extending wall of such slot interrupts the light beam.

VIny accordance with the invention, the width of they slots v16 and the speed of rotation of the motor 15 are so adjusted that the time interval between succeeding rectangular waves is equal to the time required for a cornplete cycle of cylinder operation of a test engine operated under standard conditions. the slots 16 is such that there is a preselected time interval between the leading edge and trailing edge of each rectangular wave, this 'time interval being selected so as to represent a standard interval between the time of occurrence of detonation and the time of occurrence of a reference event, such as the spark, in a test cylinder of an internal combustion engine. Of course, where other applicationsare made of the circuit, the width ofthe rectangular waves and the interval between them-can be adjusted to suit the particular conditions encountered.

, 24a, Figure 3c, atthe output of amplier 27, Likewise, ,A Y

The output of photoelectric vcell 12 is represented by Y the rectangular waves 20, Figure 3a. In this gure, theV interval A, which represents the time between successive rectangular waves, corresponds to a complete cycle of,A cylinder operation, and the interval B, which is the widthy of the rectangular wave, represents the time interval between the occurrence of detonation and the occurrence of spark or other reference event in a cylinder of a test engine.

The output of the cell 12 is fed through an amplilier 21 to a differentiating circuit 22, which produces anjoutput representing the time rate of-change of amplitude of the rectangular waves 20. Accordingly, the output of this circuit is a series of sharp pulses 23, Figure 3b, of

one polarity corresponding in time with the leading edges of the rectangular waves 20 together with a series of Y sharp pulses 24 of opposite polarity corresponding in time with the trailing edges of the respective rectangular waves 20. The output of diiierentiating circuit 22 is fed toa pair of rectiliers 25 and 26 of opposite polarity. Rectifier 25 passes only the negative pulses 24 and eliminates positive pulses 23 while rectifier 26 passes the positive pulses 23 and rejects the negative vpulses 24.

The output of rectifier 25 is fed through an amplifier 27 to an output circuit 28. Assuming that the amplifier 27 has an odd number of stages, such as one, ,the nega. tive pulses 24 are inverted, thatY is, shifted in phaseKA through an angle of and appear as positive pulses Patented Apr. 8, 1958 Furthermore, the width of these pulses appear with `the same polarity in the output circuit 28, as indicated by Pulses 24a in Figure 3f.

The output of rectifier 26 isfed, in succession, through n.180" phasefshifting icircuit29-iandfan amplifier 301to the output circuit 28. Positive pulses 23 are inverted or shiftedthrough -atphase I-an'gle-'of ,180 by the circuit 29 and appear as negative pulses 23a, Figure 3d, attheoutput of `this circuit.` Assuming lthat`amplifier 30 has an odd number of stages, such as one, `the pulses 23a' are again inverted orf-shifted in phase through an angle of 180, and appear again as positive pulses -23b, V,Figure 3e, at the output of amplifier 30 and r`at the voutput -of circuit 28, asindicatedby Figure 3f.

vIt'will be evident that the output `,of circuitr28 consists of 4successive sets 23 b, r24a of. sharpgpulses, each Vset being separated byithexdistanceA, Figures `3a and 3f,frepresent,

ing the time interval betweenssuccessive cycles off cylinder operation, .the pulses 23b, 24av of .each :setfbeing separated bythe distance B, AFigure 3a and V3f, representing the width 1of rectangular waves 20 Aand the time interval between occurrence of `detonation and the occurrence `of spark or other Aindex variablein an internal combustion engine. It will be evident, therefore, that the pulses 23.6, 24a `can be fed `to an instrument of the type Idisclosed by the'aforementioned copending applications to readily=aud Vquickly calibrate same.

Cil

:A` detailedcircuit construction in accordance rwith the l block diagram of `Figure 1` .is `shown by Figure 2. This circuit includes a conventional power supply including a line plug 31, switch 32, power `transformer 33, :rectifier 34,` pilot light 35, `filter chokes 36, 37, `filter condensers 38, 39 and bleederresistances V40, 41. It will vkbenoted with a grid resistance 47, anda constant potential being maintained `upon the control grid of tube 46 by aresistor 48 connected `to a 'positive power supply line 49.V .The anode of tube 44 is connected directly 'to line 49 `while its cathode is connected directly to the cathode of tube 46 and to ground through a bias Vresistor 50. The anode of `tube 46 is connected to line 49 through Aa resistance 51 and to a terminal 52 through a condenser 53. It will be apparent that the tubes 44, 46 function as voltage amplifiers with the output thereof appearing at the anode of tube 46. Y

d Resistor 51 and condenser 53 constitute'the differentiat ing circuit 22 of Figure 1 and the time constant ofthis circuitis so selected as toprovide a sharp pulse when the Amplifier tube 58 forms a part of the phase shifting circuit29'an`d is provided with a grid 'resistor' 63, ac'athode biasing resistor 64, and an anode voltage dropping resistor 65 connected to a positive power supply terminal 66. The output of this tube, which is inverted in phase with respect to its input, is -fed through a coupling condenser 67 to the control grid of a tube 68 forming a part of the amplifier 30. Tube 68 is provided with agrid resistor 69, a cathode bias resistor 70 and an anode voltage dropping lresistor 71,*theoutput being taken from the anode of the latter tube and passed through a coupling' condenser 72 to a terminal v73 forming a part of output circuit 28.V

It will be noted that phase shifting is accomplished in the described circuit by utilizing one amplifier stage between the output of rectifier 25 and the circuit 28 while two stages rare inserted between the output of rectifier 26 and circuit28, each stage providing a phase shiftof 1807. Since the differentiated pulses fed through the rectifiers 25, 26 are originally ofopposite polarity, and there is one more stage in ,the amplifier associated with one rectifier than in the amplifier associated with the other rectifier, the outputs of the amplifierswill have` thesa'me phase relationship. This holds true if the number of stages inthe two amplifiers differ-by 3 or vany other odd integer. Of course, other types of phase shifting 'circuits can be utilized, such as resistance-capacitance circuits, rather `than thel particularv arrangement of amplifier tubes herein disclosed. Y p

The output circuit Y28 includes a `ground terminal 75, a -fixed resistance 76 connected between terminals 63,75 andajfixed resistance 77 connected between the terminals, 73, 75. It will be understood, therefore, that the output of the amplifiers 27, 30 can vbe separately withdrawn, if desired,v or these outputs can'lbe combined if such is desirable. A

. It will be apparent that we have achieved the objects of our invention in providing a Calibrating circuit for instruments wherein the time interval between a reference event and the occurrence of detonation is measured during each Vcycle of operation of a test engine.

Furthermore, we have shown a pulse producing circuit and associated .rectangular wave generator which have independent utility aside from the calibration of detonation measuring instruments. p

While the invention has been Vdescribed in connection with a present, `preferred embodiment thereof, itis to be understood that this description is illustrativepnly and is notintended to limit` the invention.

amplified leading or trailing edge of a `rectangular wave is impressed upon the circuit. To this end, resistance 51 can have value of 100,000 ohms and'condenser 53 can have a value of .0001` microfarad. The differentiated pulses appear between terminal 52 and ground, a fixed re sistance 54 being provided between these points.

Terminal 52 is. connected to the cathode of a rectifierV tube `55, the anode of which is connectedto the control grid of a tube 5,6. Terminal 52 is also connected to the anode of a rectifier tubel'57, the cathodefo which is connected to the control grid of Va tube St.r Rectifier tube Y passes pulses of negative polarityy but rejects pulses of positive polarity while Vrectifier tubev 57 passes pulses of posi-` tive polarity but 4rejectspulses of' negative polarity.

'ruberse is included in amuser zi, nie tube being pio.V

vided'with a grid resistor `59, a cathode bias resister 60, and tananode voltage 4dropping resistor 61. The. "output of amplifier tube-56, which is inverted in phasewithl'r'e spect; to its inpunis fed through a coupling condenser 62 to an output terminali?, of the outptcircuitZ-St polarity at Vthe end of each rectangular wave, a pair of rectifiers of opposite rpolarity fed by said differentiating circuit for separating said differentiated pulses, a first amplifier responsive to one set of rectified pulses, and a second amplifier responsive to the other `set of rectified puises, the number of stages in one amplifier being'greater than the number of stages in the other amplifier by an odd integer. l

2. Apparatus for producing spaced sets of pulses, each Y set including apair of spaced pulses, which comprises,

` rectangunlar wave photoelectric. cell output, tliewid'th of in combination, a photoelectric cell', a light sou'rce trained on said cell, a circular shutter having` a` plurality of radial slots forined therein interposed between said sourcer and .said c'ell ,",rr'1e'ans for rotating'fsaid shutter. to produce a said slots and the speed of's'aidl motor bein'g'lso adjusted that the width of said rectangularv waves represents'the 2,sso,191

desired time interval between each pair of pulses and the stituting the sole impediment between said source and said cell, an amplifier fed by said photoelectric cell, a differentiating circuit fed by said amplifier, a pair of rectifiers of opposite polarity fed by said diiferentiating circuit, a rst amplier responsive to the output of one rectaner, and a second amplier responsive to the output of the other rectifier, the number of stages in said iirst and second amplifiers diiering by an odd integer.

3. Apparatus for producing spaced sets of pulses, each set including a pair of spaced pulses, which comprises, in combination, a photoelectric cell, a light source trained on said cell, a circular shutter having a plurality of radial slots formed therein interposed between said source and said cell, means for rotating said shutter to produce a rectangular wave photoelectric cell output, the width of said slots and speed of said motor being so adjusted that the width of said rectangular waves represents the desired time interval between each pair of pulses and the interval between rectangular waves represents the desired time interval between sets of pulses, an amplifier fed by said photoelectric cell, a differentiating circuit vfed by said amplifier, a pair of rectifiers of opposite polarity fed by said differentiating circuit, the output of one rectifier being diiterentiated pulses of one polarity representing the leading edges of said rectangular waves, the output of the other rectifier having dilerentiated pulses of opposite polarity representing the trailing edges of said rectangular waves, an output circuit, means for feeding one set of differentiated pulses to said output circuit, and means of inverting the other set ofditferentiated pulses with respect to said one set then feeding the invertedpulses to said output circuit.

4. Apparatus for calibrating a detonation meter Wherein a time interval is measured, in each of a number of operating cycles, between an electrical pulse representing detonation and an electrical impulse representing an index time, said apparatus including a photoelectric cell, means for directing a beam of parallel light rays upon said cell, a circular shutter having a plurality of slots formed therein, the edges of said slots being defined by radii of said shutter, and said shutter being interposed in said light beam, means for rotating said shutter, the width of said slots and the speed of said rotating means being so adjusted that the width of said rectangular waves represents a predetermined interval corresponding to the interval between the occurrence of said index time and detonation in an internal combustion engine under standard conditions, and the interval between said rectangular waves corresponding to the time required for a single complete cycle of cylinder operation, and said shutter constituting the sole impediment between said source and said cell, and a circuit fed by said photoelectric cell to produce sharp electrical pulses at times corresponding to the beginning and end of each rectangular wave.

5. Apparatus for calibrating a detonation meter wherein a time interval is measured, in each ofr a number of operating cycles, between an electrical pulse representing detonation and an electrical impulse representing the spark, said apparatus including a photoelectric cell, means for directing a beam of parallel light rays upon said cell, a circular shutter having a plurality of slots formed therein, the edges of said slots being defined by radii of said shutter, and said shutter being interposed in said light beam, means for rotating said shutter, the Width of said slots and the speed of said rotating means being so adjusted that the width of said rectangular waves represents a predetermined interval corresponding to the interval between the occurrence of spark and detonation in an internal combustion engine under standard conditions, and the interval between said rectangular waves corresponding to the time required for a single complete cycle of cylinder operation, a differentiating circuit fed by said photoelectric cell, a pair of rectifiers of opposite polarity fed by said differentiating circuit, the output of one rectitier being differentiated pulses of one polarity representing the leading edges of said rectangular waves and the output of the other rectifier being differentiated pulses of opposite polarity representing the trailing edges of said rectangular waves, an output circuit, means for feeding one set of differentiated pulses to said output circuit, and means for inverting the other Vset of differentiated pulses with respect to said one and then feeding the inverted pulses to said output circuit.

6. Apparatus for calibrating a detonation meter wherein a time interval is measured, in each of a number of operating cycles, between an electrical pulse representing detonation and an electrical impulse representing the spark, said apparatus including a photoelectric cell, means for directing a beam of parallel light rays upon said cell, and a circular shutter having a plurality of slots formed therein, the edges of said slots being defined by radii of said shutter, and said shutter being interposed in said light beam, means for rotating said shutter, the'width of said slots and the speed of said rotating means being so adjusted that the width of said rectangular waves represents a predetermined interval corresponding to the interval between the occurrence of spark and detonation in an internal combustion engine under standard conditions, the interval between said rectangular waves corresponding to the time required for a single complete cycle of cylinder operation.

References Cited in the file of this patent UNITED STATES PATENTS 

